Claims that an “alkaline” diet can whittle the waistline, curb inflammatory conditions and even cure cancer is growing. Yet the evidence supporting any of these health claims is pretty slim. Here’s what you need to know about this, yet another, fad.

What is it?

The theory goes something like this: too much acid in the body creates a breeding ground for disease.

Proponents of the diet advocate that by eating 80 per cent alkaline foods and 20 per cent acidic foods, you’ll create a pH balance in your body that is optimal for health.

To achieve the 80/20 ratio means placing meat, dairy products, wheat and some grains in the undesirable “acid-producing” category. You can also forget about indulging in coffee, tea, sugar, soft drinks and alcohol, leaving you with what is essentially a vegetarian regime based on a wide variety of fresh vegetables, fruits, and selected legumes, grains and nuts.

These foods are believed to help the body maintain its normal blood pH level at approximately 7.4 (a slightly alkaline state), in which bodily processes, say advocates, function at their best within this range.

But do we really need to alkalise our body?

“No, the kidneys and lungs control our pH balance, not our diet,” says Dr Douglas Samuel, gastroenterologist and senior lecturer in medicine at University of Sydney and NSW, who is sceptical of the pH balance argument.

“The alkaline diet theory is just that – a theory – waiting to be proven by quality research. It’s simply not possible to change the body to an alkaline environment. The body is an extremely efficient system that works 24/7 to keep the body in a slightly alkaline state at all times regardless of what we eat,” adds Samuel.

Besides, measuring the pH of foods does not reflect the acid or alkali load they provide to the body after the complex process of metabolism and excretion. “It is near impossible to predict the impact of a food on acid-base balance. This means the commonly promoted food charts have clear errors,” warns Samuel. For example, foods such as orange and lemon juice are acidic in their natural state but add a total alkaline load after they have been metabolised in the body.

The proof is in the pee

The theory surrounding the alkaline diet has been around since the 19th century when the French biologist, Claude Bernard, discovered that changing the diet of rabbits from herbivore (mainly plant) to carnivore (mainly meat) turned their urine from more alkaline to more acid. Based on Bernard’s findings, studies using urine testing soared in order to quantify the acid or base-forming potential of foods, which eventually led to a bunch of related diets: The PH miracle, Acid-Alkaline Diet, and Eating the Alkaline Way (recently championed by the likes of Victoria Beckham).


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And while promoters of these diets claim that foods can change the body’s pH (which isn’t true), the pH of urine, however does vary – and rightly so, as this clearly demonstrates how clever our bodies are at maintaining tight control of blood pH despite what food we throw at it. After all, that’s what our kidneys and lungs are designed to do: excrete excess acid or alkali.

It’s promoted as an osteoporosis preventer. Acidic diets increase calcium loss in urine, but there is no evidence from superior quality balance studies that increasing the diet acid load has any effect on total body calcium or causes osteoporosis.

The claim that high-protein foods, such as red meat tend to be the most acid forming and can lead to kidney stones (both calcium based and uric acid stones) may have merit. “Uric acid-based kidney stones can dissolve in an alkaline urine and may do well on the alkaline diet, however uric acid stones only make up about 5 per cent of kidney stones,” says Kidney Health Australia’s Medical Director, A/Professor Tim Mathew. “If you have calcium stones these may also be helped with a low protein diet.”

Says Mathew: “Studies have suggested that protein is not necessarily a major contributor to acid load and concerns about the impact of protein on acid production appear to be minor compared with the alkalinising effects of fruits and vegetables. However the calcium content of the urine is increased in people on a high animal protein intake and this may add to the risk of forming new calcium stones.”

The claim that cancer cells will survive in an acidic environment is far from the truth. While this may be true in the laboratory setting, this is not the case in the human body.

“There’s no specific diet that can treat or cure cancer,” says Clare Hughes, Nutrition Program Manager at the New South Wales Cancer Council in Australia. There is, however a link between red meat, in particular processed meats, with some cancers, but it doesn’t mean you need to avoid red meat all together,” adds Hughes.

The Cancer Council recommends people eat not more than 455 grams of cooked lean red meat each week. This means no more than 65 grams a day, or larger portions every second day.

“There is clear evidence that a healthy diet helps to reduce cancer risk,” they say.

The Cancer Council also recommends eating fresh fruits and vegetables, as well as wholegrain and fibre-rich foods; limiting or avoiding alcohol and foods; maintaining a healthy body weight and being physically active.

Bottom line

“If the diet’s promotion encourages people to eat more fruit and vegetables, then it’s a good thing,” says Dr Samuel.

But restricting yourself to certain food groups will mean people miss out on essential nutrients such as calcium, B vitamins, iron and zinc and protein, which are really important.

It would be dangerous to try to do this diet long term because of those nutritional deficiencies. The best diet includes a wide variety of nutritious foods every day from the five key groups.